The contribution of electronically excited states to the radiation chemistry of organic systems
The absorption of 160 nm light by cyclohexane in mixtures of cyclohexane, benzene and tetraphenylmethylenediamine results in an emission spectrum consisting of the simultaneous fluorescence from all three components. A mechanism for the development of this spectrum and its dependence on benzene concentration is constructed and shown to be quantitatively consistent with the results of independent measurements on the separate components. In the absence of tetraphenylmethylenediamine, the quenching of cyclohexane fluorescence by benzene is found to be well represented by the standard diffusion model but with important contributions from transient'' terms. The fluorescence from both cyclohexane and benzene in their irradiated mixtures has been studied as a function of benzene concentration from {approx equal}0.005 M to 0.1 M. The quenching of the cyclohexane emission by benzene is found to be significantly greater than obtains under optical excitation conditions suggesting an important role for benzene as a scavenger of the geminate ion-pair precursor of the fluorescing state of cyclohexane. From diffusion models, a lower bound is established for the scavenging rate constant. Minima have been located in the excitation spectra of neat cyclohexane and 2,3-dimethylbutane at approximately the positions of their ionization potentials. The implications is that electron + positive ion neutralizations generate excited neutral states at energies lower than the ionization threshold. 17 refs.,
- Research Organization:
- Minnesota Univ., Minneapolis, MN (USA). Dept. of Chemistry
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- FG02-85ER13404
- OSTI ID:
- 6764782
- Report Number(s):
- DOE/ER/13404-5; ON: DE91001328
- Country of Publication:
- United States
- Language:
- English
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